This invention relates to a swivel hitch structure for associating implements, and particularly agricultural implements such as plows and the like, with a pulling or towing machine such as a tractor.
Plows and other agricultural implements are currently associated with pulling machines, such as tractors, by means of hitch devices which allow such implements to rotate about a horizontal axis only, i.e. the implements are not permitted to turn about a vertical axis. In other words, in the instance of a tractor pulling a plow type of implement, the plow can rotate exclusively about a horizontal axis, i.e. can be lowered for plowing and tilted up for transport, no rotational movement being provided about a vertical axis (i.e. a swinging movement from side to side in a horizontal plane) while the plow is in its lowered or working position.
This represents a first and not negligible shortcoming inasmuch as in specially severe soil conditions, particularly in rocky soils abundant with large stones, or as the tractor is turning, the plow would naturally tend, as it will be apparent, to take an offset attitude with respect to the tractor centerline; in other terms, it would tend to swing sideways and take an attitude of least pulling effort. Therefore, the very fact that the plow is forced to keep in line with the tractor, with no allowance made for it to move regularly and continuously to a position of least effort, does represent a major inconvenience, since it is a cause of energy waste as well as of poor overall performance.
There are known, as the expert in the art will surely recognize, devices for associating implements with pulling machines such as to provide a swivelling action. However, such devices are not entirely exempt from drawbacks which render their application unreliable. Furthermore, it should be noted, although the experts are already well aware of the problem, that such known devices cannot be mounted to tractors of the articulated type.